Answers to PS #1 - Classes at U. of L.

3. What point groups result from the combination of two intersecting mirror planes at:
a) 90° b) 60° c) 45° d) 30° to each other? Hint: make all the planes vertical.
4. What point groups result from the combination of two intersecting twofold axes at:
a) 90° b) 60° c) 45° d) 30° to each other? Hint: make both 2-folds perpendicular to z.
5. An atom in an orthorhombic unit cell has fractional xyz coordinates (0.1, 0.15, 0.20). Give the coordinates of a second
atom in the cell that is related to the first by each of the following (do each separately, i.e. 5 new positions in all):
a) body centering b) a center of symmetry at the origin
c) a 2 axis parallel to z and passing through the origin d) a 21 axis parallel to z and passing through the origin
e) A-centering
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